1. Field of the Invention
This disclosed invention relates to those instruments specifically designed and constructed to fit through small openings and remotely measure distances in cavities remote therefrom.
2. Description of the Prior Art
Many types of cavities, like underground mines and caves, are not readily accessible to humans. Our invention is directed to remotely measuring dimensions in these types of cavities without humans actually being in the cavity. Many types of devices are known which measure distances without physically employing a solid measuring device placed between the end points whose distances therebetween is desired to be determined. Some of these systems employ reflected waves, like laser, radar, or sound waves, and determine the distance under observation by noting the time interval it takes the wave to travel both ways and multiplying it by the known velocity of the particular wave used. Because of the inaccuracies that would be caused by the readings from the received reflected waves, we do not employ this principle to measure distance. However, the U.S. Pat. Nos. 3,180,205 (Hepper), 3,848,999 (Dall'Armi), and 3,620,625 (Tegholm) disclose systems which in someway or another do employ this principle.
Television cameras have been employed in systems used to measure distances. One example is found in U.S. Pat. No. 4,063,283 (Rider et al) wherein digitized signals from a television camera are processed by a computer which collects reflected laser beams (col. 2, lines 43 et seq.).
Our invention is different from all of these systems in that it is used to measure distances in underground cavities through a borehole in the earth; it does not employ reflected waves to determine the distance; it does use two spaced light beams that are superimposed on a common object, a television camera, and the principles of trigonometry to arrive at the distances to be determined. Since the television camera and intersecting light beam may be selectively oriented to face in almost any direction in the cavity, many distance measurements can be made within the cavity to profile a complex surface therein. None of the known prior art employs such a system to reveal the detail surface configuration under investigation rather than the average distances obtained from reflected pulses of energy.